liu.seSearch for publications in DiVA
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Mineralisation of organic matter in coastal sediments at different frequency and duration of resuspension
Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
2006 (English)In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, Vol. 70, no 1-2, 317-325 p.Article in journal (Refereed) Published
Abstract [en]

Coastal sediments represent sites of major importance for many biogeochemical processes, including organic matter mineralisation. These sediments are frequently subjected to intermittent physical forcing resulting in resuspension, which potentially influences sediment processes. In this study we investigated how the frequency and duration of resuspension events affect organic matter mineralisation rates, by creating conditions where the resuspension effect was as isolated as possible from other factors possibly affecting the mineralisation rate. Results show that continuous resuspension or resuspension in 12 h intervals double the mineralisation rates compared to sediments not subjected to water turbulence (2.0 ± 0.2 vs. 1.1 ± 0.3 μmol ΣCO2 (g d.w.)−1 d−1). However, when subjected to short resuspension events (5 s) once every 24 or 48 h the sediment mineralisation rate were enhanced even more, to 5.2 ± 0.3 μmol ΣCO2 (g d.w.)−1 d−1. Longer intervals between resuspension events (72–96 h) did not affect the mineralisation rate compared to no water turbulence. This indicates that resuspension enhances mineralisation rates, and that even very short resuspension events can influence sediment carbon and nutrient cycling to a large extent if occurring often enough. Hence, sediment mineralisation rate measurements without resuspension may significantly underestimate mineralisation rates. However, given our results, it is possible that continuous low-level shear stress in coastal areas may be enough to stimulate mineralisation, and then specific events with increased shear stress and resuspension may not cause any additional enhancement. Therefore, to illuminate potential effects of resuspension on mineralisation under field conditions, more information about the level of shear stress that is required to affect mineralisation rates is needed.

Place, publisher, year, edition, pages
2006. Vol. 70, no 1-2, 317-325 p.
Keyword [en]
resuspension; mineralisation; sediment respiration; organic matter degradation; northwest Baltic Proper
National Category
Oceanography, Hydrology, Water Resources
Identifiers
URN: urn:nbn:se:liu:diva-14301DOI: 10.1016/j.ecss.2006.06.022OAI: oai:DiVA.org:liu-14301DiVA: diva2:23155
Available from: 2007-02-13 Created: 2007-02-13 Last updated: 2009-06-04
In thesis
1. Mineralisation rates of natural organic matter in surface sediments affected by physical forces
Open this publication in new window or tab >>Mineralisation rates of natural organic matter in surface sediments affected by physical forces
2006 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [sv]

Nedbrytning av organiskt material är en nyckelfaktor som påverkar omvandlingar av de många grundämnen som utgör eller är associerade till just organiskt material. En stor del av nedbrytningen av akvatiskt organiskt material (OM) sker i gränsskiktet mellan sediment och vatten. Eftersom så många biogeokemiska cykler styrs av nedbrytningen av OM är det viktigt att ha kunskap om processer och påverkansfaktorer både på mikro- och makronivå. Mineraliseringshastigheten av OM är en vanligt förekommande mätparameter, men vanligtvis inkluderar mätningarna inte de naturliga processer som kan påverka nedbrytnings-hastigheterna, t.ex. fysiska krafter.

Syftet med den här studien är att studera mineraliseringshastigheten av det OM som finns naturligt i ytsediment i söt- och brackvatten när det utsätts för fysiska krafter som orsakar förändringar i redox-förhållanden, resuspension eller advektivt porvattenflöde. Fem

laborativa experiment har utförts för att belysa syftet:

Åldrat ytsediment från en sötvattens å utsattes för olika redox förhållanden där oxisk respiration, sulfatreduktion respektive metanogenes gynnades. Resultaten visade ingen skillnad i mineraliseringshastighet beroende på behandling. Detta motsäger studier utförda i marina miljöer, där anoxiska förhållanden ger en lägre mineraliseringshastighet än oxiska.

Vidare gjordes två studier på brackvattensediment där effekten av resuspension var i centrum. Den ena studien fokuserade på frekvens och varaktighet av resuspensionstiderna, den andra på olika typer av sediment. Studierna visade att väldigt korta resuspensionstider med upp till 48 timmars stillhet mellan varje resuspension ökade mineraliseringstakten med fem gånger jämfört med diffusivt utbyte, och mer än dubblerades i jämförelse med kontinuerlig resuspension eller resuspension i långa perioder. Resuspensionen under kort tid var troligen gynnande då resuspension fysiskt stör bildningen av stabila bakteriesamhällen. Mineraliseringshastigheterna i sediment som domineras av väldigt fin, fin eller medium sand visade lika hastigheter, medan grov sand visade en signifikant lägre mineraliseringshastighet. Likheterna mellan de tre första sedimenttyperna kan dock ha påverkats av tillgång på lättnedbrytbart OM då sediment och vatten hämtades in under en algblomning.

Till sist studerades effekten på mineraliseringshastigheten av advektivt porvattenflöde. Detta gjordes på åldrat sediment dels från en sötvattensbäck dels från en brackvattenstrand. Inget av de två sedimenttyperna visade någon skillnad i mineraliseringshastighet i jämförelse med diffusivt styrda system. Det är i motsats till tidigare marina studier, men är i linje med den första studien, där mineraliseringshastigheten var oberoende av redox-förhållande.

Den generella slutsatsen från den här studien är nödvändigheten att studera samma aspekter i olika typer av akvatiska system, eftersom responsen verkar vara annorlunda beroende på system, t.ex. söt- brack- och saltvatten. Faktorer som kan förklara de här skillnaderna finns ännu inte, vilket gör att småskaliga studier och modeller blir viktiga verktyg för att utreda detta.

Abstract [en]

Organic matter mineralisation is a key parameter that affects most other element transformations associated with organic matter. A substantial part of aquatic organic matter (OM) mineralisation takes place at the interface between sediment and water. Understanding OM mineralisation is important at both the micro and macro scales, since it drives many biogeochemical cycles. OM mineralisation rates are widely measured, but generally not all the natural factors possibly affecting the rates, such as physical forcing, are considered.

This thesis examines the mineralisation rates of indigenous OM in fresh and brackish surface sediments, subjected to different physical forces inducing changed redox conditions, resuspension, and advective pore water flow. Five experiments were performed to this end.

Aged surface sediment from a freshwater river was subjected to different redox conditions favouring oxic respiration, sulphate reduction, and methanogenesis, respectively. Results indicated no difference in mineralisation rate irrespective of treatment. This contradicts what has been found in marine environments, where anoxic mineralisation rates are lower than oxic ones.

Further, two studies of resuspension of brackish sediments were performed, one addressing the impact of the frequency and duration of the resuspension events, and the other addressing the impact of resuspension on different types of sediments. The studies found that very brief resuspension events followed by calm periods of up to 48 h increased mineralisation rates by five times compared to diffusion, and more than doubled the rate compared to continuous or long-term resuspension. The short-term events were possibly favoured because resuspension physically disturbs the arrangement of a stable bacteria community. Mineralisation rates on sediments dominated by very fine, fine, or medium-grained sand were the same, while coarse sand displayed a significantly lower rate. The similar rates of the three first sediment types could stem from access to labile OM, due to an ongoing algae bloom when the sediment and water samples were collected.

Finally, the effect of advective pore water flow on aged sediment from one fresh and one brackish sediment was studied. Neither of the sediments displayed a mineralisation rate different from those occurring in incubations in which only diffusive exchange occurred. This contradicts the findings of previous marine studies, but is in line with the first study, which did not detect different mineralisation rates irrespective of redox conditions.

The general conclusion is that it is necessary to study the same physical forces in different aquatic environments, since responses appear to differ, for example, between freshwater, brackish, and marine environments. Factors explaining these differences have not yet been expressed, making small-scale studies and modelling a challenge for future research.

Place, publisher, year, edition, pages
Tema vatten i natur och samhälle, 2006. 52 p.
Series
Tema V report (online), ISSN 1652-4268 ; 30
Keyword
Sediment, Organic matter mineralisation, Organic matter degradation, Redox, Electron acceptor, Resuspension, Advective pore water flow
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:liu:diva-8332 (URN)91-85643-76-9 (ISBN)
Presentation
2006-06-01, Elysion, Hus T, Campus Valla, Linköpings universitet, Linköping, 13:15 (English)
Opponent
Supervisors
Available from: 2007-02-13 Created: 2007-02-13 Last updated: 2009-03-12

Open Access in DiVA

No full text

Other links

Publisher's full textLink to Licentiate thesis

Authority records BETA

Ståhlberg, CarinaBastviken, DavidSvensson, Bo H.Rahm, Lars

Search in DiVA

By author/editor
Ståhlberg, CarinaBastviken, DavidSvensson, Bo H.Rahm, Lars
By organisation
Department of Water and Environmental StudiesFaculty of Arts and Sciences
Oceanography, Hydrology, Water Resources

Search outside of DiVA

GoogleGoogle Scholar

doi
urn-nbn

Altmetric score

doi
urn-nbn
Total: 292 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf